Graphene surface induced specific self-assembly of poly(3-hexylthiophene) for nanohybrid optoelectronics: from first-principles calculation to experimental characterizations

We demonstrate a specific chain alignment of pi-conjugated polythiophenes on the graphene monolayer via first-principles calculation and experimental characterizations. The effects of alkyl chain and thiophene backbone in poly(3-hexylthiophene) (P3HT) on the specific binding energy and molecular configuration on the graphene monolayer are independently investigated. Due to specific pi-pi interaction and van der Waals interaction between P3HT and graphene monolayer, two different configurations (edge-on and face-on) of P3HT are formed on the graphene, while only edge-on configuration of P3HT is found on the indium tin oxide (ITO). These behaviors are verified by using atomic force microscopy (AFM) and transmission electron microscopy (TEM). We also explore the molecular orientation of P3HT chains on the graphene using 2D grazing incidence X-ray diffraction (GIXD) to obtain molecular orientation features over a large area. Our results will provide a strategy to create next-generation polymer-graphene nanohybrid optoelectronic devices.